P0123Powertrain
Throttle position sensor A circuit high input
Where to start
The throttle sensor reads higher than the actual opening — the control unit thinks the pedal is pressed harder. Check the connector and the wire. If the code appeared right after washing the engine, let everything dry and clear the code before replacing anything.
What to watch in live data
A code is not a diagnosis. It says which check failed, not which part to replace. Clearing it without repair only means the car will report it again in a few trips.
How to put together a report a mechanic will actually read
We have a detailed piece on thisThrottle position sensor: P0121, P0122, P0123 and P2135
Step by stepUnstable idle — how to find the cause
How the code is built
Letter — the systemPowertrain: engine and transmission
Common or the maker's ownGeneric code: the same on every car
Which part of the engineFuel and air metering
Number of the faultThe serial number inside that group — it does not say how serious the fault is
All codes in «Throttle and accelerator pedal»
How the app helps
CarScan reads this code from your car through an OBD-II adapter, shows whether it is active now or only stored, names the module that reported it, and puts it into a plain-text report for your mechanic.